Estimating the economic burden of mastitis and antimicrobial use in a commercial dairy system using the animal health loss envelope framework.

Introduction: Mastitis is one of the most economically important diseases affecting dairy production systems, generating substantial losses through reduced milk production, treatment costs, and premature animal removal. However, farm-level economic assessments based on longitudinal management data remain limited in many low- and middle-income countries. Methods: This study applied the Animal Health Loss Envelope (AHLE) framework to estimate the economic impact of mastitis using four years (2022-2025) of routinely collected data from a large commercial dairy farm in Zambia. Farm records were analyzed to quantify disease occurrence, treatment outcomes, antimicrobial use, production losses, and health-related expenditures associated with mastitis management. Results: The herd recorded an average of 768 clinical mastitis cases annually among approximately 1,809 lactating cows, corresponding to an average incidence of 42.46%. Although recovery rates were high (95.1%), mastitis resulted in substantial productivity losses through discarded milk, mortality, and mastitis-related culling. Economic impacts were driven by both direct expenditures on treatment and preventive interventions, including antimicrobial therapies, diagnostics, hygiene measures, and vaccination, as well as indirect losses associated with reduced marketable milk and animal removal. Antimicrobial use intensity (AMUI) showed temporal variation across production periods, with higher AMUI values observed during months with increased mastitis incidence. Annual antimicrobial expenditure exceeded ZMW 834,833.00 (USD 34,784.70) while AMR-related diagnostics and mitigation investments (vaccination, disinfectants, biosecurity) exceeded ZMW 2,977,667.00 (USD 193,638.80). Mastitis caused large indirect losses through discarded milk (up to 234,445.25 L/year) and delayed reproduction (395-day calving interval). The final estimated loss of ZMW 6,786,211.88 (USD 282,758.83) resulted from the combined effects of direct disease management costs and indirect productivity losses observed per year. Conclusion: The results illustrate how mastitis and treatment-refractory infections contribute significantly to the Animal Health Loss Envelope (AHLE) and provide foundational data for future Productivity-adjusted-life-years (PALYs) estimations and cost-effectiveness analyses of AMR mitigation strategies. Our study demonstrates the practical applicability of the GBADs AHLE framework in real-world dairy systems.